1. Field of the Invention
The present invention relates to an electronic packaging apparatus or mounter for mounting electronic components such as chips or the like on component support mediums such as printed-circuit boards, and more particularly to an electronic packaging apparatus for moving nozzles which attract electronic components under suction with accurate timing when or after the electronic components are mounted on component support mediums.
2. Description of the Prior Art
There have heretofore been proposed various electronic packaging apparatus or mounters for mounting electronic components such as chips or the like on printed-circuit boards. FIG. 1 of the accompanying drawings schematically shows a conventional packaging machine for drawing a carrier tape with a plurality of chips bonded thereto at longitudinal intervals therealong from a cassette, and mounting chips on a printed-circuit board or the like through an attracting head on a turntable.
More specifically, as shown in FIG. 1, a component supply unit 1 movable in the directions indicated by the arrows A, A' carries a plurality of cassettes 2 each housing a roll of carrier tape with a plurality of chips bonded thereto at longitudinal intervals therealong. The component supply unit 1 is moved to bring the tape outlet port of one of the cassettes 2 to an attracting position or a first station P.sub.1 on a turntable 3 which is positioned in front of the component supply unit 1.
The turntable 3 can be indexed successively to twelve positions, i.e., first through twelve stations P.sub.1 .about.P.sub.12, which are spaced at equal angular intervals for effective respective operations.
In the first station P.sub.1, an electronic component such as a chip is attracted from a carrier tape under vacuum by an attracting head 4. Then, the turntable 3 is angularly moved an angle .theta. of 30.degree. to bring the electronic component to the second station P.sub.2 in which the electronic component is centered. In the next third station P.sub.3, the vertical position of the electronic component is measured by a laterally positioned imaging camera or a phototransistor.
In the fourth station P.sub.4, an imaging camera or the like positioned below the turntable 3 detects whether there is an electronic component or not and also recognizes the shape of the electronic component. No operation is effected on the electronic component in the fifth station P.sub.5. In the sixth station P.sub.6, if the electronic component is angularly displaced with respect to the attracting head 4 as detected by the shape recognition, then the electronic component is turned .DELTA..theta..degree. into a proper angular position with respect to the attracting head 4. In the seventh station P.sub.7, the electronic component attracted by the attracting head 4 is mounted on a printed-circuit board or the like.
Specifically, a component support medium such as a printed-circuit board or the like is fed onto an XY table 5 by a loading lifter 6. After the electronic component attracted by the attracting head 4 is mounted on the component support medium in the seventh station P.sub.7, the component support medium is delivered from the XY table 5 onto an unloading lifter 7.
No process is carried out in the next eighth station P.sub.8. The turntable 3 carries a plurality of attracting head nozzles selectable depending on the shape and size of an electronic component to be mounted. The ninth station P.sub.9 checks which nozzle is being currently used.
When the checking process in the ninth station P.sub.9 is finished, the type of an attracting head nozzle which will be used in a next mounting cycle has already been known. In the tenth station P.sub.10, the nozzle to be used in the next mounting cycle is selected and brought into a front position on the turntable 3. In the eleventh station P.sub.11, an external actuator gear is held in mesh with a gear on the selected nozzle, and turns the nozzle gear back to a predetermined angular position so that the nozzle gear will properly mesh with a gear when the nozzle attracts an electronic component. The twelfth station P.sub.12 confirms the operation carried out in the eleventh station P.sub.11. Then, the selected nozzle of the attracting head is turned to the attracting position in the first station P.sub.1 where the attracting head attracts a next electronic component.
Each of the attracting heads 4 on the turntable 3 which are indexable successively to the above stations P.sub.1 .about.P.sub.12 will be described below with reference to FIGS. 2 and 3.
The attracting head 4 has a substantially cylindrical nozzle block 8, a spindle 9 mounted centrally on the nozzle block 8 for rotating the nozzle block 8 thereabout, and a gear 10 mounted on an upper surface of the nozzle block 8.
A plurality of external actuator mechanisms 11 are located respectively in some of the stations P.sub.1 .about.P.sub.11. For example, an external actuator mechanism 11 is positioned in the tenth station P.sub.10, moves in the direction indicated by the arrow C (see FIG. 3) into mesh with the gear 10, and rotates the nozzle block 8 counterclockwise, for example, about the spindle 9.
The actuator mechanism 11 comprises a channel-shaped bearing 12, a drive shaft 13 rotatably mounted on the bearing 12, and a gear 14 mounted on the drive shaft 13 between upper and lower arms of the bearing 12. An actuator such as a motor (not shown) is coupled to the drive shaft 13 for rotating the drive shaft 13 clockwise, for example, about its own axis.
As shown in FIG. 2, attracting nozzles 15a, 15b, . . . , 15e having respective different nozzle diameters matching types and sizes of components to be attracted are mounted on the nozzle block 8 at equally angularly spaced five positions, respectively. Each of the nozzles 15a, 15b, . . . , 15e is rotatably supported on the nozzle block 8 by upper and lower bearings 16a, 16b. Gears 17a, 17b, . . . , 17e are coaxially mounted on the respective nozzles 15a, 15b, . . . , 15e above the gear 10. These gears 17a, 17b, . . . , 17e can be held in mesh with the gear 14 of the actuator mechanism 11 for rotation thereby.
To center or correct the angular position of an electronic component on the turntable 3 in the second, sixth, and eleventh stations P.sub.2, P.sub.6, P.sub.11, etc., the gear 14 of the actuator mechanism 11 in each of these stations is brought into mesh with one of the gears 17a.about.17e coupled respectively to the nozzles 15a.about.15e, and rotated to rotate the corresponding one of the nozzles 15a.about.15e. To select one of the nozzles in the tenth station P.sub.10, the gear 14 of the actuator mechanism 11 in the tenth station P.sub.10 is brought into mesh with the gear 10, and rotated to rotate the nozzle block 8.
In order to attract or release an electronic component 18 such as a chip in the first and seventh stations P.sub.1, P.sub.7, it is necessary to vertically move the tip end of one of the nozzles 15a.about.15e to a part supply position on the turntable 3 and to vertically move the electronic component 18 attracted to the nozzle to the surface of a component support medium such as a printed-circuit board or the like, as shown in FIG. 4.
A mechanism for vertically moving the nozzles 15a.about.15e will be described below with reference to FIG. 4. The mechanism serves to vertically move the nozzles 15a.about.15e with respect to the nozzle block 8. The mechanism includes a link 27 coupled to a cam follower which is held against a cam surface of a cam 25 that is mounted on a shaft 24 rotatable by a cam drive motor 23 of a main drive assembly of the packaging machine. The link 27 converts rotary motion of the cam 25 into vertical movement of the nozzles 15a.about.15e in the directions indicated by the arrows D, D'. As the nozzles 15a.about.15e vertically move, a valve 22 disposed in each of the nozzles 15a.about.15e operates. The valve 22 comprises a three-way valve having a first valve port connected by a tube 21a to a vacuum pump 19 actuatable by a vacuum pump motor 20, a second valve port connected by a tube 21b and a restriction 28 to a high-pressure air inlet port 26, and a third valve port connected to one of the nozzles 15a.about.15e. The tip ends of the nozzles 15a.about.15e are open.
When each of the nozzles 15a.about.15e, i.e., the valve 22 disposed therein, is not pressed downwardly by the link 27, the vacuum pump 19 is actuated. If no electronic component 18 is attracted to the tip end of each of the nozzles 15a.about.15e, then air is drawn into the open tip end of each of the nozzles 15a.about.15e. If an electronic component 18 is attracted to the tip end of each of the nozzles 15a.about.15e, then the first valve port of the valve 22 in each of the nozzles 15a.about.15e is opened and the second valve port thereof is closed for developing a vacuum in each of the nozzles 15a.about.15e.
To attract an electronic component 18 with each of the nozzles 15a.about.15e and mount the electronic component 18 on a printed-circuit board 29 on the XY table 5, the valve in each of the nozzles 15a.about.15e is operated by the cam 25 and the link 27 to shut off the air flow toward the vacuum pump 19. Specifically, the first valve port of the valve 22 is closed, and the second valve port thereof is opened. Air under high pressure supplied from the high-pressure air inlet port 26 is restricted by the restriction 28 and then supplied through the tube 21b and the valve 22 to each of the nozzles 15a.about.15e, which discharge the air through their open tip ends.
The first and second valve ports of the valve 22 are selectively opened and closed in the above manner through a mechanical arrangement actuatable when the nozzles 15a.about.15e are pressed by the cam 25 and the link 27.
The angular displacement of the cam 27, the vertical position or height of each of the nozzles 15a.about.15e, the pressure in each of the nozzles 15a.about.15e, and the time at which the electronic component 18 is released from each of the nozzles 15a.about.15e are shown in FIGS. 5A through 5C. FIGS. 5A through 5C illustrate a relatively long mounting cycle.
FIG. 5A shows the angular displacement of the cam 27 and FIG. 5B shows the vertical position of each of the nozzles 15a.about.15e. While the cam 27 is being angularly moved from 0.degree. to 180.degree.+.DELTA..degree., each of the nozzles 15a.about.15e is in the upper end of its vertical stroke. After elapse of a time T.sub.5 from the end of the period in which each of the nozzles 15a.about.15e is in the upper end of its vertical stroke, each of the nozzles 15a.about.15e reaches the lower end of its vertical stroke. When each of the nozzles 15a.about.15e descends to a suitable position (h) from the upper surface of the printed-circuit board 29, i.e., the lower end of its vertical stroke, the valve 22 in each of the nozzles 15a.about.15e is operated to start introducing air under high pressure into each of the nozzles 15a.about.15e. At this time, the cam 25 is angularly positioned at (A) in FIG. 5A, which position is referred to as a vacuum breaking position. The pressure in each of the nozzles 15a.about.15e is shown in FIG. 5C.
As shown in FIG. 5C, since the response of air is very slow, the pressure in each of the nozzles 15a.about.15e varies from a vacuum condition in the position (h) through an atmospheric pressure condition to an air discharge condition in a time T.sub.3. When air is discharged from each of the nozzles 15a.about.15e after elapse of the time T.sub.3, each of the nozzles 15a.about.15e is on its downward stroke. The pressure which is applied to the electronic component 18 upon downward movement of each of the nozzles 15a.about.15e is greater than the pressure applied when air is discharged. Therefore, the electronic component 18 is prevented from being ejected from the tip end of each of the nozzles 15a.about.15e.
After elapse of a time T.sub.1 from the vacuum breaking position (A), the electronic component 18 on the tip end of each of the nozzles 15a.about.15e reaches the upper surface of the printed-circuit board 29. The electronic component 18 is now mounted on the printed-circuit board 29. After elapse of a time T.sub.2 from the vacuum breaking position (A), each of the nozzles 15a.about.15e starts being elevated. At this time, air is being discharged from the open tip end of each of the nozzles 15a.about.15e. Thus, no force is exerted to lift the mounted electronic component 18 upon ascent of each of the nozzles 15a.about.15e. When each of the nozzles 15a.about.15e is lifted to the position (h), the valve 22 is operated to cut off the flow of the high-pressure air after elapse of a time T.sub.4 from the vacuum breaking position (A). Then, the atmospheric pressure condition is developed in each of the nozzles 15a.about.15e in a time T.sub.6 after elapse of the time T.sub.4.
No problem arises if the mounting cycle is relatively long with T.sub.2 &gt;T.sub.3 as shown in FIGS. 5A, 5B, and 5C. The mounting cycle has to be varied depending on the size and type of electronic components 18 to be held by the nozzles 15a.about.15e. If the mounting cycle is relatively short with T.sub.2 .ltoreq.T.sub.3, then the angular displacement of the cam 27, the vertical position of each of the nozzles 15a.about.15e, the pressure in each of the nozzles 15a.about.15e are changed for releasing the electronic component 18 from each of the nozzles 15a.about.15e, as shown in FIGS. 6A, 6B, and 6C.
As the mounting cycle becomes shorter, the cam 25 rotates faster. When the cam 25 is angularly moved to the vacuum breaking position (A) which is a fixed position determined by the cam 25, the valve 22 in each of the nozzles 15a.about.15e is operated by the link 27 to change from the vacuum condition to the air discharge condition. With the shorter mounting cycle, the times T.sub.1, T.sub.2 shown in FIGS. 5A.about.5C become shorter times T.sub.1 ', T.sub.2 ', respectively, as shown in FIGS. 6A.about.6C. Since the response of air is low, however, the time T.sub.3 is not made shorter at the same rate as the times T.sub.1, T.sub.2, but remains the same (T.sub.3 =T.sub.3 ').
As shown in FIGS. 6B and 6C, when the electronic component 18 attracted to each of the nozzles 15a.about.15e reaches a mounting point at the lower end of the downward stroke thereof after elapse of the time T.sub.1 ', the atmospheric pressure condition is developed in each of the nozzles 15a.about.15e. Even after elapse of the time T.sub.2 ', no air discharge condition is developed in each of the nozzles 15a.about.15e, and each of the nozzles 15a.about.15e starts ascending. Since the time T.sub.3 ' has not yet elapsed at this time, the electronic component 18 is not released from the tip end of each of the nozzles 15a.about.15e, and is lifted with each of the nozzles 15a.about.15e as they move upwardly. Then, the air discharge condition is developed in each of the nozzles 15a.about.15e on their upward movement, causing the electronic component 18 to drop onto the printed-circuit board 29. Therefore, the electronic component 18 supported by each of the nozzles 15a.about.15e cannot properly be mounted on the printed-circuit board 29.
Such a drawback would be eliminated by not fixing the vacuum breaking position (A) but producing a cam with a different vacuum breaking position (A) each time the mounting cycle is varied. However, if ten different mounting cycles are available to choose from, then ten different cams corresponding to the mounting cycles would have to be prepared and made available.